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Springboot使用Filter

Springboot中使用Filter有两种方式,注解方式,注册bean方式

一、注解@WebFilter

1、实现Filter接口(javax.servlet)

2、添加@WebFilter注解

3、启动类添加@ServletComponentScan注解

附上代码:

第一个Filter:

@Slf4j
@WebFilter(filterName = "filter1", urlPatterns = {"/url1/*"})
public class Filter1_Filter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("do filter1");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }

}

第二个Filter:

@Slf4j
@WebFilter(filterName = "filter2", urlPatterns = {"/url2/*"})
public class Filter2_Filter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("do filter2");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }

}

启动类:


@SpringBootApplication
@ServletComponentScan
public class MyApplication {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication .class, args);
    }

}

下面说说我踩过的坑

1、不加@ServletComponentScan注解无法注入Filter,这个注解的作用就是去扫描@WebServlet、@WebFilter、@WebListener这类特殊注解。如果不加,spring容器是不会主动扫描的

2、多个Filter的执行顺序,说出来你可能不信,这种注解方式实现的Filter是通过Filter的类名首字母来控制执行顺序的,像Filter1_Filter就比Filter2_Filter先执行。但网上一些资料说,当Filter数量很多时,是没有明确的执行顺序的,所以这种方式还是放弃吧,推荐第二种

二、注册bean

1、实现Filter接口

2、注册Filter

下面附上代码:

第一个Filter:


@Slf4j
public class Filter1 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("do filter1");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }

}

第二个Filter:


@Slf4j
public class Filter2 implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("do filter2");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }

}

注册类:


@Configuration
public class FilterConfig {

    @Bean
    public Filter filter1(){
        return new Filter1();
    }

    @Bean
    public Filter filter2(){
        return new Filter2();
    }

    @Bean
    public FilterRegistrationBean setFilter1() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(filter1());
        filterRegistrationBean.addUrlPatterns("/url1/*");
        filterRegistrationBean.setOrder(1);   //order的数值越小,在所有的filter中优先级越高
        return filterRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean setFilter2(){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(filter2());
        filterRegistrationBean.addUrlPatterns("/url2/*");
        filterRegistrationBean.setOrder(2);   //order的数值越小,在所有的filter中优先级越高
        return filterRegistrationBean;
    }

}

这种方式就比较严谨了,通过filterRegistrationBean.setOrder(1)设置执行顺序亲测有效

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